Melissa,
Open up AdobeScriptLibrary1.jsx in a text editor (Adobe's ESTK is a great one for editing scripts).
Look at around line 368 or search for:
TYPES.DEFAULT_CONTACTSHEET
you should see a line like:
TYPES.DEFAULT_CONTACTSHEET = "JPG,JPEG,TIF,TIFF,GIF,AI,PSD,PDF,";
Just add eps, epsf to the list.
TYPES.DEFAULT_CONTACTSHEET = "JPG,JPEG,TIF,TIFF,GIF,AI,PSD,PDF,EPS,EPSF";
Then restart bridge.
That will do it for you.
Bob